Process of catalytically hydeogen



Patented July 20, 1937 UNITED STATES ATENT OFFICE PROCESS OFCATALYTICALLY HYDROGENL. ATING PHENOLS Wilbur A. Lazier, New CastleCounty, DeL, as. signor to E. I. du Pont de Nemours & Company, ton, Del,a corporation of Delaware No Drawing. Application May 21, 19:5 1 SerialNo. 22.559

26 Claims. (01. 269-153) This invention relates to processes for thecata- 5 nols to the corresponding cyclic secondary alcohols by means 01'catalysts consisting of hydrogenating metals or their oxides admixedwith or chemically combined with more acidic oxides. Specifically, thisinvention relates to the hydrogenation of phenols with chromitecatalysts.

This application is a continuation in part of my co-pending applicationsSerial No. 456,298 filed May 27, 1930, and Serial No. 715,509, filedMarch 14, 1934.

Considerable work has been done in the field of catalysis with a view todeveloping emclent materials for the hydrogenation of such unsaturatedcompounds as the olefines. unsaturated fats and fatty acids, benzene andits derivatives,

and a large number of other compounds containing unsaturated functions;such as the nitro compounds, nitriles, and heterocyclic unsaturatedring-compounds. Most of this work has been based on the classicaldiscovery of Sabatier that finely divided metallic nickel is capable ofcausing the union of hydrogen with these compounds. The method has beenfurther expanded and supplemented by the work of Ipatief ontheapplication of high pressures to these reactions.

Extensiveresearch has been carried out heretofore with the result thatseveral different modifications of the preparation of hydrogenationcatalysts have been developed, the most common of which involve theprecipitation and reduction of nickel or copper hydroxides orcarbonates, re-v duction of nickel and copper oxides prepared byignition of the nitrates, anodic oxidation followed by reduction,heating to their decomposition temperatures of certain organic saltsofhydrogenating metals, the 1 chemical erosion of alloys, andelectrochemical deposition of hydrogenating metals.

.' Furthermore, various methods .of reductionv have been proposed,ranging from the ordinary dry reduction with hydrogen to reduction in aninert liquid vehicle or in the presence of the oil or other substanceundergoing hydrogenation.

The nuclear hydrogenation ofphenols generalhas been practised for manyyears in themanufacture of cyclohexanol from phenol. The proc ess'may becarried out in the vapor phase as first described by Sabatier (Catalysisin Organic 55 Chemistry, Sabatier-Reid, 1923, page 166) or indecomposition temperature.

, 1y is by no means a new process. In fact, it.

the liquid phase as outlined by Brochet (U. S. 1,247,629).

In either case the catalyst consists of metallic nickel prepared byreduction of the oxide or carbonate. Phenols have also been hydrogenated5 in the presence of the oxides and sulfides of chromium molybdenum, andtungsten for the purpose of converting them into the correspondingaromatic hydrocarbons. So far as I am aware, no one has heretoforesucceeded in e1- 10 fecting the nuclear hydrogenation of a phenol in thepresence of a diflicultly reducible oxide catalyst or a reducible oxidemaintained in an unreduced condition. In fact, Connor and Adkins (J. A.C. S. 53, 1094 (1931)) have recently stated 15 that the copper chromitecatalyst is not active towards cyanides' or towards benzene nuclei andthus ofiers a means of selective hydrogenation of compounds containingthese groups which are otherwise readily reducible over nickelcatalysts. They state further that toluene, phenol, aniline, and furoicacid could not be hydrogenated under the conditions described for thehydrogenation of (other) compounds".

Contrary to this statement, it has now been found according to thepresent invention that chromite catalysts are effective agents for usein the nuclear hydrogenation of phenols and make possible theapplication of the inherent advantages of these catalysts to animportant class of hydrogenation reactions. According to the presentinvention a large number of monoe nuclear and polynuclear phenols may behydrogenated to the corresponding secondary alcohols in th presence ofcopper'chromite and reduced 85 nickel chromite.

This invention, accordingly, has as an objectto carry out the catalytichydrogenation of phenols by the use of highly eflicient hydrogenatingmetal or metal oxide catalysts promoted by the addition of acidic oxidessuch as chromium oxide. A further object is to provide a. process forthe hydrogenation of phenols in either liquid or vapor phase by the useof catalysts prepared by heating a multiple chromate of a hydrogenatingmetal and a nitrogen base to its spontaneous It is a specific object tocarry out the hydrogenation of phenols by the use of reduced chromitecatalysts derived from double chromates of ammonia and a hydrogenatingmetal. Other objects will appear hereinafter.

, This inventionin its general aspects comprises the employment in-theliquid or gas phase 1 hydrogenation of phenols, oi catalysts prepared 55by associating or chemically combining hydrogenating metal oxides withacidic metal oxides. Thecatalyst compositions utilized in'accordancewith the present invention may consist of purely physical mixtures. Theymay, on the other hand, consist of complex salts containing thehydrogenating oxide and the acidic promoter oxide in chemicalcombination. Thus, within the scope of the invention are included suchcompositions as mixtures of copper oxide and chromium oxide, andcompounds such as copper chromite.

The specific nature and purpose of the invention requires that thecatalytic mass contain an acidic metal oxide associated with or combinedwith a hydrogenating metal and/or metal oxide. The preparation ofcatalysts suitable for use in the present invention conforms generallyto the following methods which will be illustrated by nickel-chromiumoxide catalysts. It will be understood that these methods may be appliedin the same way to the preparation of catalysts containing hydrogenatingmetals other than nickel or their oxides, and containing acidic oxidesother than chromium oxides. The illustrative methods of preparation ofthe catalysts are as follows:

(1) The hydrogenating metals or their oxides may be simply mixed withthe acidic oxides in any desirable proportions, thus equal parts ofnickel oxide and chromium oxide may be admixed to form a suitablecatalyst.

(2) Concentrated solutions of nickel chloride and neutral ammoniumchromate are permitted to react at room temperature. Upon standing, agreen crystalline salt of nickel ammonium chromate is formed. Thesolution is filtered with suction and the precipitate dried and heatedslightly to start the decomposition reaction, which thereafter proceedsspontaneously with the evolution of sufiicient heat to leave a glowingresidue probably consisting of combined nickel oxide and chromium oxide.This composition may be subsequently further reduced with hydrogen toproduce the desired catalyst.

(3) Two-molar solutions of nickel nitrate and ammonium chromate aremixed in equivalent amounts and heated to boiling, whereupon abrlck-recLprecipitate of basic nickel ammonium chromate is separated.Ammonia may be added to neutralize the acid solution formed by theprecipitation and greatly improves the yield. As in method (2), thedouble ammonium compound is heated slightly to occasion spontaneousdecomposition and the resulting ignited product may be further reducedwith hydrogen.

(4) Nickel oxide or carbonate is digested with chromic acid untilcompletely dissolved. On evaporating the solution to dryness, theresidue is reduced with hydrogen, or is first heated to redness,representing a temperature in the vicinity of 800 C., to convert it tothe chromite form, followed by hydrogen reduction.

The methods described above are equally applicable to the preparation ofchromites of hydrogenating metals other than nickel, for example, copperand silver and other members of the ferrous metal group, such as ironand cobalt.

(5) A very active copper chromite preparation is formed by theinteraction of equimolecular proportions of copper nitrate and neutralammonium chromate solutions, followed by ignition. Basic copper ammoniumchromate is formed by the precipitation, which yields a complex mixtureof copper oxide and copper'chromite on gentle ignition. This product isactive for the hydrogenation of phenols and other unsaturated compoundswithout further treatment, and is therefore a very convenienthydrogenation catalyst to prepare. As in the preparation of the nickelcatalysts, the copper oxide-copper chromite catalyst may be furtherreduced with hydrogen to yield a catalyst mass containing metalliccopper commingled with copper oxide and copper chromite. The copperchromite catalyst, prepared by ignition of the double chromate, withouthaving been subjected to further reduction by hydrogen is highly emcientfor the purposes of the invention.

I have disclosed above the preparation of chromite catalysts by thespontaneous decomposition of double ammonium chromates. By the termnitrogen base" I include, besides ammoniuin compounds, organicderivatives such as salts of pyridine, aniline and methylamine. Whenheated, these organic derivatives behave in a manner similar to theammonium derivatives and yield chromites, which, upon reduction, possessthe same catalytic properties. Various formulae have been assigned tothese double salts by individual investigators. Cold concentratedsolutions of nickel chloride and ammonium chromate yield a green salt towhich the formula:

(NH4) zNi (CrO4) 2.61120 has been assigned, while more dilute solutionsat higher temperatures give rise to-the formation of a brick-redprecipitate probably having the formula:

(um) macro) 2.2m.

Both of these compounds decompose spontaneously on heating and yield aproduct in which chromium is present in the trivalent form.

The nitrogen base compounds, typified by nickel ammonium chromate, arepreferably heated slowly to start the reaction after which theydecompose spontaneously, leaving a residue of nickel chromite. Thespontaneous decomposition temperature will vary for the differentcompounds, but in general, it may be said to range from 200 C. to 400C.ing composition with hydrogen may be carried out at 400 C. to 600 C.,preferably at 500 C.

The simple chromates, typified by nickel chromate prepared asillustrated in method (4), may be reduced to the chromite by igniting ata temperature somewhat higher than is required for the nitrogen basemultiple chromates. Ignition of chromates of this type takes place atabout 600 to 800 C., although higher temperatures may be used in specialcases. Where further reduction-by means of hydrogen is desired, it maybe Reduction of the resulteffected at about 400 to 800 C. and preferablyat about 500 C.

It is possible to carry out the reduction of chromates of either of theabove types by exposing them to the action of hydrogen at elevatedtemperature, without having submitted the material to previous ignition.Thus, catalysts may be prepared by subjecting the chromates to hydrogenat a temperature of 400 to 600 C. for a period of time sufficient toconvert the chromates into compositions containing either freehydrogenating metal or its oxide associated or combined with chromiumoxide containing chromium in the trivalent form. It is generallydesirable, however, to first ignite the material to reduce the chromateto chromite, since the resulting composition is more compact andconvenient to handle than would otherwise be the case.

In general, any other hydrogenating metal or its oxide can besubstituted for nickel, this class including zinc, copper, silver,cobalt and iron.

' my invention, the following examples which are included merely forpurposes of illustration and not as a limitation, disclose specificmethods used in carrying the invention into practice and the improved.results accruing from; its use.

Example I A nickel chromite hydrogenation catalyst was prepared asfollows: 8'72 g. of'nickel nitrate (NiNO3.6H2O) and 300 g. of chromiumtrioxide (0203) were dissolved in 900 cc. of distilled water. Nickelammonium chromate was precipitated by adding rapidly with vigorousstirring 600 cc. of 28.3 per cent aqueous ammonia. The precipitate wasfiltered from the'mother liquor, dried at C., and decomposed to thechromite by heating at 350 C. for four hours; The nickel chromite thusobtained was ground to 100 mesh and reduced in hydrogen for 18 hours at350 C. and at 540 C. for 1.5 hours longer. After cooling in hydrogen andsweeping the system out with car- Hydrogenation was carried out withvigorous agitation at a hydrogen, pressure of about 1000 pounds persquare inch and at a temperature of about 185 C. Hydrogen absorption wasrapid under these conditions and the reaction was complete in about twohours. Distillation of the flltered product gave a yield of about 95 percent of cyclohexanol.

In a similar manner, mixed cresols may be hydrogenated to thecorresponding methyl cyclohexanols and .xylenols to the correspondingdimethyl cyclohexanols.

Example II Two hundred and twenty-eight grams of pure nickel hydroxidewas suspended in water and treated with 200 g. of chromic anhydride. Theresulting paste was filtered, dried, and ignited four hours at 400 C.Five grams of the residual nickel chromite composition was reduced 24hours with hydrogen at 500 C. The resulting mass was cooled andtransferred without exposure to air to a vessel containing 200 g. of 85per cent phenol in water. The mixture was heated and agitated for twohours with pure hydrogen at 800 lbs. pressure. Hydrogenation began at C.and was quite rapid at 170 C. Pure cyclohexanol was formed under theseconditions and the yield was almost quantitative.

Crude meta cresol, known commercially as.

cresylic acid, may be hydrogenated effectively at about 200 C. whensimilar technique is used. Likewise, betanaphthol may be readilyhydrogenated to yield the correspondingtetrahydro monia.

parts of chromic acid were dissolved in 1668 parts of water and 34 partsof. anhydrous ammonia was added with agitation during a period of 15 to30 minutes. After washing the precipitate by decantation, 161 parts of.chromic acid was added to redissolve the precipitate and the solutionwas made up to a volume equal to the original copper suliate-chromicacid solution. Copper ammonium chromate was reprecipitated by theaddition of 32 parts 01' anhydrous amand dried, after which it wasignited ,at 400 C. The resulting chromitewas then extracted twice bystirring for 15 minutes each time in a solution of 100' parts of glacialacetic acid and 900 parts of water. After extraction, the chromite waswashed free from acid, filtered and dried at C. and screened to 20 meshsize.

One hundred and seventy-six grams of an-' hydrous phenol, 24 grams ofwater, and 14 grams of copper chromite, prepared as described above,were charged into an autoclave equipped for agitation under highpressure. The charge was heated to 240 to 260 C. and agitated for fivehours under a hydrogen pressure of 2300 to 3500 pounds per square inch.Hydrogen was absorbed rapidly and was completed in about 2.5 hours.Distillation of the product gave an amount of pure cyclohexanolequivalent to a 97 per cent conversion of the phenol.

Under similar conditions o-cresol was converted into the corresponding2-methyl cyclohexanol.

Example IV One of the importantadvantages of using copper chromitecatalyst forthe hydrogenation of phenols is that in complex structurescontaining more than one kind of unsaturation. it may be possible tohydrogenate selectively the phenol nucleus without attacking the other.unsaturated parts of the molecule.

This precipitate was washed, filtered The point in quesion is,

illustrated by the hydrogenation of para phenyl phenol to phenyl'cyclohexanol. -When-hydrogenated in the presence of a nickel catalyst,para phenyl phenol yields cyclohexyl cyclohexanol through hydrogenationof both the. phenyl and phenol rings. On the contrary, copper chromiteis inert towards hydrogenation of the phenyl ring but allows attack onthe phenol ring, thus forming as the product a phenyl cyclohexanol.

A catalyst consisting of copper chromite supported on kieselguhr wasprepared exactly as described in Example III, except that 205 g.'ofkieselguhr was added to the copper nitrate-chromic acid solution andkept in suspension by vigorous agitation during precipitation withammonia. The catalyst thus prepared consisted oi! copper chromitesupported on kieselguhr, the two components being present in about equalproportions. Fifteen grams of the catalyst thus prepared and 150 g.ofp-phenyl phenol were placed in a shaking autoclave and hydrogen wascated certain definite conditions of temperature,

pressure, gas concentration, amounts or materials,

. duration of reactions, etc., it is. to be understood that any and allof these may be varied widely within the scope of my invention, sincethe particular conditions of operation are governed largely by thespecific reaction catalyzed, the materials treated, and the catalystselected for a given reaction.

In carrying out the processes of the present invention the temperaturesused may vary over a considerable range, depending on the exactcomposition of the catalyst used. In general, the hydrogenation ofphenols with nickel chromite catalyst will'take place at lowertemperatures than when copper chromite is used. The operationtemperature for chromite catalysts generally is about 120 to 300 C.While pressure is not a critical factor, it is preferable to carry outphenol hydrogenations under superatmospheric pressure; for example, inthe range of 10 to 500 atmospheres.

It will be apparent from the examples given that the catalysts of myinvention have mariy valuable applications. Although I have describedtheir use in certain selected liquid and vapor phase hydrogenationswhich illustrate their particularly advantageous properties, they arecapable of use in the hydrogenation of many other phenolic bodies. ThusI may hydrogenate phenols such as ordinary phenol, cresols, xylenols,alphaand beta-naphthol, diphenylols, and crude tar acids containinglarge concentrations of phenols. The present invention also contemplatesa new process for the hydrogenation of phenols directly to cyclicketones. Since copper chromite may be used in the vapor phase at fairlyhigh temperatures and low pressures, these conditions are ideal forconverting the cyciohexanols first formed from the phenols byhydrogenation into the corresponding ketones by dehydrogenation.

As many apparently and widely different embodiments of this inventionmay be made without departing from the spirit and scope thereof, it isto be understood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of a hydrogenating catalyst comprising as an essentialingredient a hydrogenating metal oxide associated with an acidic metaloxide. l

2. The .process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a. phenol inthe presence of a hydrogenating catalyst comprising as an essentialingredient a hydrogenating metal oxide associated with an acidic metaloxide, which 5. The process of catalytically hydrogenating the nucleusof a hydroxyph nyl group which comprises reacting hydrogen and a phenolin the presence of a copper chromite catalyst at a temthe nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of catalyst comprising essentially nickel oxide associatedwith chromium oxide.

7. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of a nickel chromite catalyst.

8. The process of catalytically .hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of a catalyst prepared by heating a multiple chromate of anitrogen base and a. hydrogenating metal to its spontaneousdecomposition temperature and thereafter subjecting the resultingcomposition to partial reduction.

9. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting i'rvdrogen and a phenol inthe presence of a catalyst prepared by heating the compound resultingfrom the precipitation of nickel chromate in the presence of ammonia toits spontaneous decomposition temperature and thereafter subjecting theresulting composition to partial reduction.

10. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol at atemperature above 120 0., and at a pressure in excess of 10 atmospheresin the presence of a cat-- resulting composition in a stream of hydrogenat about 500 C.

12. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of a catalyst prepared by heating a multiple chromate of anitrogen base and nickel to its spontaneous decomposition temperatureand thereafter subjecting the resulting composition to partialreduction.

13. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol at atemperature above 120 C., and at a pressure in excess of 10 atmospheresin the presence of a catalyst prepared by heating a multiple chromate ofa nitrogen base and copper to its spontaneous decomposition temperatureand thereafter subjecting the resulting composition to partialreduction.

14. The processdf catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting hydrogen and a phenol inthe presence of a catalyst prepared by heating a multiple chromate of anitrogen base and a hydrogenating metal to its spontaneous decompositiontemperature and thereafter subjecting the resulting composition to apartial hydrogen reduction.

- the nucleus of a hydroxyphenyl group which comprises reacting phenoland hydrogen at a temperature between and 300 C. in the presence of acatalyst comprising essentially a hydrogenating metal oxide associatedwith an acidic metal oxide.

16. The process of catalytically hydrogenating the nucleus ofa'hydroxyphenyl group which com-.

prises reacting phenol andhydrogen at a temperature of about 120 toabout 200 C. in the presence of a nickel chromite catalyst.

1'7. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting phenol and hydrogen at atemperature of about 240 to about 260 C. in the presence of a copperchromite catalyst.

18. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises reacting phenol in a concentratedaqueous solution with hydrogen in the presence of a copper chromitehydrogenating catalyst at a temperature of about 240 to about 260 C. andat a pressure of about 2300 to about 3500 pounds per square inch andrecovering the cyclohexanol formed.

19. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which cornprises reacting hydrogen and a polynuclearphenol in the presence of a hydrogenating catalyst comprising as anessential ingredient a hydrometal oxide.

20. The process of catalytically hydrogenating.

the nucleus of a hydroxyphenyl group which comprises reacting hydrogenand a polynuclear phenol in the presence of a catalyst comprisingessentially copper oxide associated with chromium oxide.

21. The process of catalytically hydrogenating the nucleus of ahydroxyphenyl group which comprises'reacting hydrogen and a polynuclearphenol in. the presence of a copper chromite catalyst.

genating metal oxide associated with an acidic 22. The process ofpreparing a phenyl cyclohexanol which comprises carrying out a partialselective catalytic hydrogenation of a phenyl phenol in the presence ofa hydrogenating catalyst comprising as an essential ingredientahydrogenating metal oxide associated with an acidic I metal oxide.

23. The process of claim 22 wherein the catalyst is copper chromite.

24. The process of claim 22 wherein the catalyst has been partiallyreduced.

25. The process or claim 22 wherein the hydrogenating catalyst comprisesas the said essential ingredient a hydrogenating metal oxide asSO-ciated with chromium oxide.

26. The process of claim 22 wherein the catalyst comprises essentiallycopper oxide associated with chromium oxide.

p WILBUR A LAZIER.

